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Discussion Starter · #1 · (Edited)
Hello again

Hope you help me - Bike is a CB350K3

Some good mews to start - engine back in the frame (and things looking very nice).

....so I thought I'd adjust the valve clearance. Note everything is torqued down correctly / cam chain tensioned etc. and I've followed the Clymer manual.

I can't get anywhere close to the 0.002" inlet or 0.004 exhaust clearances - I'm way over these tolerances. I've rotated through the full range of valve clearance adjustment available .

A bit of background on the engine / valve train:

1) The cam is a replacement from an Italian police bike and has been machined for (2)
2) I've installed a Capellini Moto roller bearing conversion
3) I've installed new replacement rockers from CMSNL.

Very grateful for your thoughts, before I take the engine out.....(my thoughts are that the rockers are not the correct spec?)

Jonathan
 

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If you’re way over those ranges at all points in your rotation, doesn’t that mean that the cam never contacts the tappets, never opens the valves, and the rockers are somehow too high above your cylinder head? You may need to lose that Clymer.
 

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Discussion Starter · #3 ·
Thanks Pat

No - not that far out!

To clarify - full rotation of the available adjustment of the valve clearances - the valves are opened and closed by the cam.

I'd agree that the Clymer manual is probably not the best out there.

Jonathan
 

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The usual problem is too tight of clearances due to valve seat grinding so yours is odd. Did you do any valve work or valve replacement?

Do you have a picture of the cam and rockers?
 

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DSC02755.jpg

This is a fat cam with a skinny cam rocker ..... it will move the valve but will not be able to come close to the valve clearance setting. The fat cam fits in both variations of the cam box.

If this is the case you will need the fat cam rockers.
 

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Discussion Starter · #6 · (Edited)
Thanks Boomer

Hmmmm. It's the later (skinny cam).

No valve work.

The cam is the same shape (apart from no rev counter drive and being in very condition) as the one that was in it.

Unfortunately no pictures.....wish I had.

But, you might be on to something. Would I have my issue if I had "fat cam" rockers with a skinny cam? And if this was the case, is there a way to tell the difference between rocker types? The original rockers have the code 312 on them.

I'll probably drop the engine a little tomorrow, so I can take off the cam box cover. I can compare old and new rockers.

Thanks

Jonathan
 

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"But, you might be on to something. Would I have my issue if I had "fat cam" rockers with a skinny cam? And if this was the case, is there a way to tell the difference between rocker types? The original rockers have the code 312 on them."


Skinny cam with fat cam rockers goes too tight, no clearance.

Fat cam rockers just have a variety of casting numbers, skinny cam rockers have casting numbers and, as you know, Code 312.

The only cams I have seen without the tach drive are custom cams. Is it possible you have what looks like a skinny cam that has the lobes ground the same as the fat cam profile?
 

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Discussion Starter · #9 · (Edited)
Thanks Boomer.

It's 10.20pm here, so I'll have a look and take a picture in the morning, but that does look a little like my situation - I can get it closer than that with adjustment, but still a long way off.

To complicate things CMSNL list the 312 rockers for the "Police Type" general export bike and associated cam.

I'll have a good look tomorrow, and may end pulling the cam out to compare.

Thanks for your help.

Jonathan
 

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Discussion Starter · #10 · (Edited)
Morning All / Boomer

So cam cover off.

New rockers are 312s.

Just looking at the cams I can see difference - if I look at the non lifting face of the cam and measure between the main casting and this it's (steel rule so not spot on) around 4mm, on the old cam it's more like 5mm. I'll try to measure the none lifting diameter of both cams to verify this - I need to get a vernier.

The installed cam has no casting markings, whereas the old one has an I and 5 on one side and an I and an M on the other of the main body.

Some pictures:

DSCF0783.jpg

DSCF0784.jpg

Hopefully, you can see the clearance gap (I can adjust it better than this, but not close to spec)

DSCF0786.jpg

I'm thinking I might have a fat cam profile on a skinny blank - I think I've read that these exist? I have no details on the installed cam except that I purchased it as ex Italian police, though it looks almost perfect (unused?).

Again thanks for any help and guidance

Jonathan
 

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Discussion Starter · #13 ·
Thanks both - I've re-attached the pictures.

And, here is a picture of kind of where I was before I discovered my valve clearance problem:

DSCF0779.jpg

uPVC pipe just to get an idea of potential silencer length / look.

Thanks

Jonathan
 

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Nice clean work, Jonathan, looks good. Seems I asked about the seat base previously, beautiful job on the woodwork. However, you haven't posted much so we're getting the progress in bits and pieces... :(
 

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DSC02763.jpg

The so called skinny cam is on the right, doesn't look so skinny from this view. A rounded rough reading is 39.7 mm, so from the bottom of the base circle to the top of the lobe.

The so called fat cam is on the left. A rounded rough reading same as above is 36.9.

Difference of 2.8 mm and most of that is in the base circle where the valve clearances are set.
 

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DSC02765.jpg

You should be able to slide a feeler gauge down and mark it to measure the height of the casting at the bottom of the base circle. A skinny cam reads 6.2 mm a fat cam reads 4.2.
 

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Discussion Starter · #17 ·
Nice clean work, Jonathan, looks good. Seems I asked about the seat base previously, beautiful job on the woodwork. However, you haven't posted much so we're getting the progress in bits and pieces... :(
Thanks Tom

I guess I should create a project log, but the truth is I've had the bike about 2 years, and I'm just piecing together as time allows (usual constraints - family (2 boys & wife), full time job, other projects - house and audio related), so I've just kind of ambled along to this point, but with a vision in mind - it seems almost too late. And I'm not good at keeping records / photos.

I'll see if I can sort something out, after all there is still much to do.

Jonathan
 

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Discussion Starter · #18 ·
Boomer

Thanks so much for the pictures and measurements. Not sure I can do the second one (the installed cam was machined for the roller bearing conversion), however my Dad's over tomorrow with verniers and calipers, so should be able to get some measurements, and hopefully I'll know what I have.

The decision then will be to either source replacement rockers, or find a new "genuine" skinny cam, and get that machined for the roller conversion.

Really appreciate your time and help - I'll let you know how I get on.

Best wishes

Jonathan
 

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DSC02767.jpg

OK then this may be easier......

These measurements are minus the thickness of the ruler I used. Skinny cam measurement is 20.65 mm. Fat cam measurement is 22.31.

CMSL lists both cams for the police bikes and both sets of rockers.
 

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One other question Jonathan ...... did you reuse the cam sprocket off your old cam or did this cam come with it's own?

Reason I'm asking is that the two cams have different cam sprockets ..... at least the civilian cams do ....
 
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